What does au mean in the filenames of NAOs

[xyh01]

For example, O_gga_8au_100Ry_2s2p1d.orb

And, does Ry mean Rydberg here? If so, what energy is it used to describe?

Thanks a lot!

[xyh01]

Ry is used to describe cutoff energy (Ecut) and au is the unit of cutoff radius (Rcut).

Got this from SG15-Version1p0_AllOrbitals-Version2p0/8_O_DZP/info.